LDO (Low Dropout Regulator) is a low dropout linear voltage regulator, widely used in voltage conversion for various electronic devices and automotive electronics. It offers high cost-effectiveness and flexible usage. By thoroughly explaining the key parameters of LDOs, clarifying testing methods, and interpreting the data sheet curves, engineers can quickly understand product specifications and performance, thereby improving selection efficiency.

Taking the SCT datasheet as an example, the homepage provides a wealth of product information:

Figure 1: SCT71403Q Datasheet Homepage - Product Overview

As shown in the layout, the left side under the title displays the product features, highlighting important parameters that reflect the product's performance (the red numbers correspond to the order discussed in this article). On the right side, there is a product description that provides a comprehensive overview for engineers. At the bottom, common application scenarios and typical application block diagrams are shown.

Below, we will interpret 15 common key performance parameters:

1. Input Voltage
2. Output Voltage
3. Accuracy
4. Output Current
5. Quiescent Current
6. Shutdown Current
7. Line Regulation
8. Load Regulation
9. Load Transient Response
10. Power Supply Rejection Ratio
11. Dropout Voltage
12. Protection Features
13. Integrated Features
14. Thermal Characteristics
15. External Component Selection

01. Input Voltage Range (Vin) ★

This refers to the range of input voltages that the LDO can accept.

By checking the specified minimum and maximum operating voltages, you can determine whether they meet the application requirements. A wide input voltage range provides some redundancy and allows for more application scenarios. Some products also support higher transient input voltages; for example, the SCT71403Q can support a transient input voltage of up to 45V, providing better protection for special needs.

02. Output Voltage (Vout)

This refers to the stable output voltage of the LDO.

LDOs typically come in fixed or adjustable output versions. Fixed versions have a set output voltage, which saves on external voltage divider resistors compared to adjustable versions, though they tend to have more part numbers, adding complexity to management.

03. Accuracy

This refers to the percentage deviation of the output voltage from its nominal value.

Different output voltage versions require attention to different accuracy levels. For fixed versions, accuracy corresponds to the output voltage tolerance, while for adjustable versions, it corresponds to the feedback voltage accuracy. Both are typically shown in the datasheet’s EC (Electrical Characteristics) table. For example, the SCT71005Q provides accuracy for two voltage versions: ±1% at room temperature and ±2% across the full temperature range.

In adjustable versions, users can configure the output voltage flexibly but must add external feedback resistors. SCT products like the SCT71405Q and SCT71005Q offer both fixed and adjustable versions for customer flexibility.